Tag Archives: tiny bubbles

Hot Water Boiler Expansion Tanks – HVAC Hydronics

Hot Water Boiler Expansion Tanks – There are two types of expansion tanks used on hot water boiler systems. The steel expansion tank and the bladder type expansion tank. These expansion tanks are used to provide a cushion for the expansion of water when it is heated. Without this cushion of air the pressure in the boiler system would rise and exceed the setting on the pressure relief valve causing the pressure relief valve to open and discharge water to relieve the pressure. It is necessary to for an HVAC technician to understand how these expansion tanks work in order to properly troubleshoot hot water boiler problems which may occur as a result of an issue with an expansion tank. One of the first things to check on a hot water boiler system when the pressure relief valve discharges water excessively is the expansion tank.

Hydronic Pump Cavitation | HVAC Water Problems

Hydronic Pump Cavitation | HVAC Water Problems

Cavitation Can Be a Serious Problem

Pump cavitation can cause severe problems to a pump if not addressed and corrected. To understand the cause of cavitation you need to understand the pressure temperature relationship of the liquid in the loop (typically water or water/glycol mix). As the water passes through the pump it changes pressure from the suction side to the discharge side of the pump. If the waters static pressure drops too much vapor is created causing tiny bubbles in the water or fluid in the loop passing through the pump. These bubbles are unstable and collapse causing severe turbulence inside the bearing assembly where the impellor is located and can damage the impellor. Cavitation is often occurring when one hears popping and crackling noises passing through pump. Cavitation can also sound like the pump is pumping rocks through the impellor. These abnormal noises are the result of these tiny bubbles collapsing. As these bubbles are forming the pump loses its ability to create the necessary head to continue circulating the fluid through the loop. Solve the problem of and the noises go away along with extended life of the pumping system.